x86: disable hpet on shutdown

If HPET was enabled by pci quirks, we use i8253 as initial clockevent
because pci quirks doesn't run until pci is initialized.

The above means the kernel (or something) is assuming HPET legacy
replacement is disabled and can use i8253 at boot.

If we used kexec, it isn't true. So, this patch disables HPET legacy
replacement for kexec in machine_shutdown().

Signed-off-by: OGAWA Hirofumi <[e-mail]>
Acked-by: Venkatesh Pallipadi <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>

arch/x86/kernel/hpet.c

···
 }
 fs_initcall(hpet_late_init);
 
+void hpet_disable(void)
+{
+	if (is_hpet_capable()) {
+		unsigned long cfg = hpet_readl(HPET_CFG);
+
+		if (hpet_legacy_int_enabled) {
+			cfg &= ~HPET_CFG_LEGACY;
+			hpet_legacy_int_enabled = 0;
+		}
+		cfg &= ~HPET_CFG_ENABLE;
+		hpet_writel(cfg, HPET_CFG);
+	}
+}
+
 #ifdef CONFIG_HPET_EMULATE_RTC
 
 /* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET

arch/x86/kernel/reboot_32.c

···
 #include <linux/reboot.h>
 #include <asm/uaccess.h>
 #include <asm/apic.h>
+#include <asm/hpet.h>
 #include <asm/desc.h>
 #include "mach_reboot.h"
 #include <asm/reboot_fixups.h>
···
 
 #ifdef CONFIG_X86_IO_APIC
 	disable_IO_APIC();
+#endif
+#ifdef CONFIG_HPET_TIMER
+	hpet_disable();
 #endif
 }
 

arch/x86/kernel/reboot_64.c

···
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/apic.h>
+#include <asm/hpet.h>
 #include <asm/gart.h>
 
 /*
···
 
 	disable_IO_APIC();
 
+#ifdef CONFIG_HPET_TIMER
+	hpet_disable();
+#endif
 	local_irq_restore(flags);
 
 	pci_iommu_shutdown();

include/asm-x86/hpet.h

···
 extern int hpet_force_user;
 extern int is_hpet_enabled(void);
 extern int hpet_enable(void);
+extern void hpet_disable(void);
 extern unsigned long hpet_readl(unsigned long a);
 extern void force_hpet_resume(void);